I've got a 4.6l 2 valve that has an intermittent stumble while under a slight load. Does not trigger check engine light. 5 of the coils are newer 4-5 yrs. Other are motorcraft age unknown. Will I have to wait til it gets bad enough to set a code, or is there another way to find out issue. I have not changed plugs yet, but probably will. Not crazy about changing them since they tend to blow out on these aluminum heads. Any suggestions are appreciated.
